During the operation of internal combustion engines which, for example, can be arranged in motor vehicles, so-called blow gas gets through a leakage between pistons and cylinders into a crankcase of the respective internal combustion engine. To prevent unacceptable overpressure within the crankcase or to prevent emission of blow-by gas into the environment, positive crankcase ventilation systems are used. Usually, such a positive ventilation system connects the crankcase by means of a vent line with a fresh gas tract of an internal combustion engine. Within the fresh gas tract, in particular downstream of a throttle valve, a relative negative pressure exists which allows that blow-by gas is sucked-in from the crankcase. Further, during the operation of the internal combustion engine, oil mist is generated. Thus, exhausted blow-by gas contains oil mist. To reduce the oil consumption of the internal combustion engine or to reduce the pollutant emission of the internal combustion engine, the positive crankcase ventilation system normally has an oil mist separator that serves for separating the oil mist carried along in the blow-by gas sucked out of the crankcase and to convey it to a suitable oil reservoir which, in particular, can involve an oil pan attached at the bottom of the crankcase.